Abstract
Abstract This article reports the composition dependent microstructural, optical and magnetic behavior of rare earth Sm3+ ions substituted nanocrystalline nickel ferrite. The formation of pure cubic spinel structure was confirmed by X-ray diffraction patterns. The average crystallite size was found to decrease with increasing Sm content because of hindered crystal growth. The field cooled (7 T) hysteresis loops at 5 K displayed large exchange bias of 2 kOe along with considerable coercive field for the smallest particles. A strong correlation between particle size, canted surface spins, vertical shift and exchange bias was observed at low temperature. The reduction in coercivity and saturation magnetization observed in room temperature hysteresis loops was attributed to nonmagnetic behavior of substituted Sm3+ ions. The existence of interparticle interaction below blocking temperature and high surface anisotropy due to disordered surface spins was confirmed by M-T protocols. The indirect allowed optical band gap was found to increase with high Sm content due to finite size effect.
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